Almost one in five Amazon delivery workers were injured during 2021, a study Tuesday said. The study was published by the Strategic Organizing Center, a coalition of four labor unions representing more than 4 million workers.

Using data that Amazon and its delivery contractors submitted to the US Occupational Safety and Health Administration in 2020 and 2021, the SOC found that workers delivering packages for Amazon delivery service partners were injured at a rate of 18.3 per 100 workers last year, up almost 40% from 2020. The small businesses that deliver packages for Amazon are known as DSPs.

“According to DSP operators and to lawsuits lodged by DSP owners across the US, Amazon sets unmanageably high quotas for delivery drivers,” the SOC’s study said. “Claims in one lawsuit state that during peak times, Amazon expected a DSP operator in Sacramento to deliver 350-400 packages per day per van. To complete this number of deliveries in a 10-hour shift, drivers would need to park, sort, deliver and document a delivery approximately once every 1 to 2 minutes.”

Amazon spokesperson Kelly Nantel contested the report’s findings, saying in a statement that the data was “cherry-picked” from fewer than 10% of the company’s delivery partners. “Safety is a priority across our network,” Nantel said, “which is why we’ve rolled out technology like innovative camera systems that have helped lead to an overall reduction in accident rates of nearly 50%, and we’ll keep investing in new safety tools to try and get better every day.”

While Amazon doesn’t hire delivery drivers directly, the company sets delivery quotas, creates delivery routes and directs drivers’ behavior with its apps and cameras on board some delivery vans. In addition to injury rates, drivers have reported they must pee in bottles to keep up with their demanding schedules, and that it’s difficult to resolve write-ups from Amazon that drivers believe may be in error. 

Amazon facilities where packages are prepared for delivery also had injury rates over 40% higher than Amazon’s warehouses, the SOC said in its report, as reported earlier Tuesday by CNBC.